Extracorporeal blood treatment involves taking the blood from a patient, treating the blood outside the patient, and returning the treated blood to the patient. Extracorporeal blood treatment (hemodialysis, hemofiltration for example) is typically used to extract undesirable matter or molecules (apheresis, plasmapheresis for example) from the patient's blood, and/or to add beneficial matter or molecules to the blood. The treatment is typically performed by sampling the patient's blood in a continuous or intermittent flow, by introducing the blood into a primary chamber of a filter that is defined, at least in part, by a semi-permeable membrane. The semi permeable membrane may selectively allow the unwanted matter contained in the blood pass through the membrane, from the primary chamber to the secondary chamber, and may selectively allow the beneficial matter contained in the liquid going into the secondary chamber pass through the membrane to the blood going into the primary chamber, according to the type of treatment.
Extracorporeal blood treatment is used with patients incapable of effectively eliminating matter from their blood. One example is a patient who is suffering from temporary or permanent kidney and/or liver failure. These and other patients may undergo extracorporeal blood treatment to add to or to eliminate matter from their blood, to maintain an acid-base balance, to eliminate excess body fluids, etc.
In the case of the aforementioned treatments of blood and methods of removing a blood component, the source of fluid is formed by the vascular circuit of the patient/donor, and the fluid is the blood of the patient/donor, which blood, pumped from an artery, is caused to circulate in a blood treatment apparatus (hemodialyzer, hemofilter, plasma filter, centrifuge, etc.) and, once freed of its impurities or having a fraction of one of its components reduced, is re-injected into a vein of the patient/donor.
Due to the geometry of a hemodialysis filter and the presence of microbubbles inside the semi-permeable membrane of the hemodialysis filter or due to the initiation of a blood clotting phenomena or other circumstance, the extracorporeal circuit and particularly the inlet of the hemodialysis filter can experience high pressure. These high pressures or high pressure transients can cause mechanical hemolysis in the red blood cells of the blood and/or malfunction or damage to the extracorporeal blood line. Thus it is desired to provide for early detection of high pressure in the extracorporeal circuit to prevent mechanical hemolysis in the red blood cells of the blood or other malfunction or damage.